---

yaml
---
r: 164472
b: refs/heads/master
c: a13ea5b
h: refs/heads/master
v: v3

[refs]

@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 1ac0cb5d0e22d5e483f56b2bc12172dec1cf7536
+refs/heads/master: a13ea5b759645a0779edc6dbfec9abfd83220844

trunk/mm/memory.c

@@ -108,6 +108,17 @@ static int __init disable_randmaps(char *s)
 }
 __setup("norandmaps", disable_randmaps);
 
+static unsigned long zero_pfn __read_mostly;
+
+/*
+ * CONFIG_MMU architectures set up ZERO_PAGE in their paging_init()
+ */
+static int __init init_zero_pfn(void)
+{
+	zero_pfn = page_to_pfn(ZERO_PAGE(0));
+	return 0;
+}
+core_initcall(init_zero_pfn);
 
 /*
  * If a p?d_bad entry is found while walking page tables, report
@@ -499,7 +510,9 @@ struct page *vm_normal_page(struct vm_area_struct *vma, unsigned long addr,
 	if (HAVE_PTE_SPECIAL) {
 		if (likely(!pte_special(pte)))
 			goto check_pfn;
-		if (!(vma->vm_flags & (VM_PFNMAP | VM_MIXEDMAP)))
+		if (vma->vm_flags & (VM_PFNMAP | VM_MIXEDMAP))
+			return NULL;
+		if (pfn != zero_pfn)
 			print_bad_pte(vma, addr, pte, NULL);
 		return NULL;
 	}
@@ -1144,9 +1157,14 @@ struct page *follow_page(struct vm_area_struct *vma, unsigned long address,
 		goto no_page;
 	if ((flags & FOLL_WRITE) && !pte_write(pte))
 		goto unlock;
+
 	page = vm_normal_page(vma, address, pte);
-	if (unlikely(!page))
-		goto bad_page;
+	if (unlikely(!page)) {
+		if ((flags & FOLL_DUMP) ||
+		    pte_pfn(pte) != zero_pfn)
+			goto bad_page;
+		page = pte_page(pte);
+	}
 
 	if (flags & FOLL_GET)
 		get_page(page);
@@ -2084,10 +2102,19 @@ static int do_wp_page(struct mm_struct *mm, struct vm_area_struct *vma,
 
 	if (unlikely(anon_vma_prepare(vma)))
 		goto oom;
-	VM_BUG_ON(old_page == ZERO_PAGE(0));
-	new_page = alloc_page_vma(GFP_HIGHUSER_MOVABLE, vma, address);
-	if (!new_page)
-		goto oom;
+
+	if (pte_pfn(orig_pte) == zero_pfn) {
+		new_page = alloc_zeroed_user_highpage_movable(vma, address);
+		if (!new_page)
+			goto oom;
+	} else {
+		new_page = alloc_page_vma(GFP_HIGHUSER_MOVABLE, vma, address);
+		if (!new_page)
+			goto oom;
+		cow_user_page(new_page, old_page, address, vma);
+	}
+	__SetPageUptodate(new_page);
+
 	/*
 	 * Don't let another task, with possibly unlocked vma,
 	 * keep the mlocked page.
@@ -2097,8 +2124,6 @@ static int do_wp_page(struct mm_struct *mm, struct vm_area_struct *vma,
 		clear_page_mlock(old_page);
 		unlock_page(old_page);
 	}
-	cow_user_page(new_page, old_page, address, vma);
-	__SetPageUptodate(new_page);
 
 	if (mem_cgroup_newpage_charge(new_page, mm, GFP_KERNEL))
 		goto oom_free_new;
@@ -2639,6 +2664,15 @@ static int do_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma,
 	spinlock_t *ptl;
 	pte_t entry;
 
+	if (HAVE_PTE_SPECIAL && !(flags & FAULT_FLAG_WRITE)) {
+		entry = pte_mkspecial(pfn_pte(zero_pfn, vma->vm_page_prot));
+		ptl = pte_lockptr(mm, pmd);
+		spin_lock(ptl);
+		if (!pte_none(*page_table))
+			goto unlock;
+		goto setpte;
+	}
+
 	/* Allocate our own private page. */
 	pte_unmap(page_table);
 
@@ -2662,6 +2696,7 @@ static int do_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma,
 
 	inc_mm_counter(mm, anon_rss);
 	page_add_new_anon_rmap(page, vma, address);
+setpte:
 	set_pte_at(mm, address, page_table, entry);
 
 	/* No need to invalidate - it was non-present before */